1 . Field of the Invention
The present invention relates to a subframe mounting bush divided into a plurality of parts to freely set a vibration insulation feature thereof and improve collision performance depending on occurrence of collision.
2 . Description of Related Art
In a vehicle, a subframe, which is mounted at a low portion of a vehicle body, has an engine and a power train of a transmission assembled thereto to support them, and has a suspension connected thereto, ensures structural rigidity of the vehicle and facilitates transfer of a load.
The subframe includes a mounting bush disposed at each mounting part so that vibrations and noise transferred from the power train and vibrations due to impact transferred from a road are not transferred.
The mounting bush 30 includes an outer pipe 32 and an inner pipe 34 mounted at the mounting part (not shown) of the subframe and a buffering rubber 36 interposed between the outer pipe 32 and the inner pipe 34, as shown in FIG. 1.
Recently, the outer pipe 32 has been formed using plastic to allow the mounting bush 30 to be easily separated from the subframe at the time of collision, in order to improve collision performance of the vehicle.
In detail, the mounting bush 30 according to the related art is press-fitted into a bush cup 38 mounted at the mounting part of the subframe in a vertical direction using an oil-hydraulic press, or the like. Here, the mounting bush 30 has a hook 32a formed at an upper end portion thereof to thereby be hooked onto an upper end of the bush cup 38, and has a flange 32b formed at a lower end portion thereof to thereby contact a lower end of the bush cup 38, such that a position thereof is fixed.
In this state, at the time of occurrence of the collision, the vehicle body is pushed, such that the inner pipe 34 coupled to the vehicle body by a bolt B is twisted. In the case in which the inner pipe 34 is twisted at a predetermined angle or more, the flange 32b formed at the lower end portion of the outer pipe 32 is fractured, such that the mounting bush 30 is separated from the subframe.
In order to prevent a problem that the mounting bush 30 is separated after assembling of the mounting bush 30 is completed, the mounting bush 30 has been controlled to have separation force of a predetermined load or more. To this end, the mounting bush 30 according to the related art has the hook 32a formed at the upper end of the outer pipe 32 to thereby be hooked onto the upper end of the bush cup 38, such that the position thereof is fixed, and has the flange 32b formed at the lower end of the outer pipe 32 to thereby contact the lower end of the bush cup 38. Therefore, when the mounting bush 30 according to the related art is press-fitted into and assembled to the bush cup 38, the hook 32a of the outer pipe 32 contacts an inner surface of the bush cup 38, such that deformation occurs inwardly by a protrusion amount of the hook 32a, thereby causing damage due to friction.
In addition, according to the related art, the mounting bush 30 is formed in an oval shape and is press-fitted into the bush cup 38 to secure separation force of the mounting bush 30.
However, since the outer pipe 32 is formed using the plastic in order to improve the collision performance, the outer pipe 32 of the mounting bush 30 formed in the oval shape is damaged due to restoring force of the buffering rubber 36, and the mounting bush 30 is not separated from the subframe due to elastic restoring force of the buffering rubber 36 at the time of the collision.
As described above, the mounting bush should be configured so as to be easily separated from the subframe at the time of the collision and so as not to be separated from the subframe at ordinary times.
However, although the mounting bush according to the related art is provided with the outer pipe formed of the plastic in order to secure the collision performance, a durability performance problem that the outer pipe is damaged when the mounting bush is press-fitted into and assembled to the bush cup of the subframe occurs. In addition, a collision performance problem that the mounting bush formed in the oval shape is not separated from the subframe at the time of the collision of the vehicle also occurs.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.